A known internal combustion engine fuel injector comprises a tubular injector body extending along a given axis; and a valve housed in a seat in the injector body and comprising a tubular valve body fixed inside the injector body seat and coaxial with the injector body. The injector has an annular chamber defined by the injector body and the valve body, which have respective annular shoulders separated by a given distance equal to the height of the annular chamber.
To form the injector, the valve body is fixed to the injector body in a given position along the axis by means of further shoulders formed on the valve and injector bodies and resting against each other, and by means of a ring nut which engages a threaded portion of the injector body and pushes the valve body axially against the injector body to keep the further shoulders in contact with each other. When connected, the injector body and valve body form, in addition to the annular chamber, a gap communicating with the annular chamber and from which high-pressure fuel may leak. To safeguard against this, the injector comprises a seal housed inside the annular chamber, at said gap, to prevent the high-pressure fuel fed into the annular chamber from leaking between the injector body and the valve body.
The Applicant has found the working life of injectors to vary widely from one injector to another, and at times to differ considerably from the working life of the engine on which they are installed.